The Research Of Stiffness And Dynamic Behavior Of Upper Bracket-Stator System Of Hydroelectric Unit

With the development of the economy and society, hydropower has become increased of concern and development as clean renewable energy. As the increasing capacity of the hydroelectric unit, the sharp increase of the hydraulic head and the expansion and complication of the powerhouse structure appears,the vibration of hydroelectric units which induces the vibration of powerhouse structure has become the important issue of the operation and design.In order to provide theoretical basis for dynamic design and vibration control of hydroelectric unit,this article presents the research on the factors of the stiffness and dynamic characteristics of the upper bracket-stator system with the stiffness and vibration characteristics of supporting structure of hydroelectric generating unit as the main research object.Using the finite element method,a model of upper bracket-stator system was established. The stator was disposed with thermal condition and the upper bracket spider was supported through 6 butterfly shaped springs. The frame members were simulated by lumped mass elements with stiffening ring and stator core besides using 3 dimensional 8 node rectangular elements.Rotor and stator adopted mass elements.The freedoms of the nodes were constrained at the joint between the frame bottom and the foundations.The sensitivity of radial stiffness of upper bracket was studied. The research showed that the dominant factor was vertical steel of upper bracket and the second factor was bearing ring. A influence curve was fit and several expressions were made to indicate that there was a difference in the solution between the coupling system and the independent upper bracket.The sensitivity of vibration characteristics of upper bracket-stator system was studied.The research showed that vertical steel has effects on the extreme value which depends on the stiffness and mass. In some cases,increase of thickness of the frame members can not increase the stiffness of the system, which should be paid more attention in the dynamic design.The reason why common value exists by bearing ring is worth investigated in the dynamic design.